Recently, technology of communicating audio information, video information, etc. on an Internet Protocol (IP) network in a real time manner such as for example video delivery, videotelephony, etc. has been spreading.
When audio information, video information, etc. are communicated in a real time manner, a large bandwidth is used continuously. This has caused a problem in which a plurality of sessions concentrate, leading to network congestion. When a plurality of communication routes (referred to as “routes” hereinafter) exist, a route with a fewer hops is usually selected regardless of congestion states of routes in IP networks. This may lead to a case where the quality of a session such as video delivery that has already been established deteriorates due to network congestion caused by a session established later.
As a method for solving this problem, a method in which a needed bandwidth is secured before the start of a session by utilizing Resource reservation Protocol (RSVP) is known.
However, when for example RSVP is utilized in video delivery, it is needed that the server apparatus that delivers videos and an information terminal device that reproduces the videos recognize the route. Also, a long period of time is taken to secure a bandwidth used for executing the session, leading to delay in starting the reproduction.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2002-152274
[Patent Document 2] Japanese Laid-open Patent Publication No. 2010-200026
[Patent Document 3] Japanese Laid-open Patent Publication No. 2012-44622